Auger mining machines employed in the coal industry use a cutting head at the end of an auger string. The rotational cutting force as well as the axial thrust force is generated at the launch vehicle and transmitted via the auger string. Due to friction losses along the length of the auger string hole depths are limited. More particularly, available cutting and conveying power decreases as the hole depth increases. Furthermore, the effectiveness of augering has been limited by the lack of both lateral and vertical "in seam" guidance systems.
Highwall mining systems generate a reaction force against a high wall face when the combined retractive forces exerted by traction jacks exceed the frictional drag imposed by the launch vehicles mass and the prevailing coefficient of friction between the ground engaging underside of the launch vehicle and the supporting ground surface.
Previous highwall and auger mining systems (including cascading continuous miner types of systems) have limited ability to impose substantial reaction forces due to the limitations in respect of these friction forces generated by the launch vehicle. This inherent weakness has the effect of limiting the mass of conveyors which may be employed in the highwall or auger mining assembly. This directly limits the maximum whole depth which can be mined. To address this shortcoming it is not uncommon for vehicles to provide "pull-out" assistance. Typically the vehicles are cat track bulldozers and similar type wheeled vehicles.